Over the last two decades more than one hundred U.S. patents have been issued for inventions involved with artificial blood pumps, energy conversion systems to power these blood pumps, and methods of their control. The prior art includes a wide range of energy sources and devices to utilize these energy sources. Extensive animal experimentation has been conducted using some of these devices and others. Presently the longest length of time during which the entire pumping function of the natural heart has been replaced by an internally implanted blood pump has been 184 days (six months) using the Jarvik-5 type of artificial heart, developed by the inventor of the electrohydraulic system with which this patent deals. The Jarvik-5 type of artificial heart is powered by compressed air and only the blood pump is implanted within the animal. Thus, the drive system which provides for the pumping of the air-driven ventricle is external to the animal. To date the longest animal survival, with an electrically powered total artificial heart, has been achieved using a Scotch yoke mechanism of mechanical diaphragm actuation in a system invented by Nat Bifano and similar to the system disclosed in U.S. Pat. No. 3,896,501. The duration of the longest survival with this electrically-powered heart has been thirty-seven days. These experiments have been conducted in calves, and only once has a total artificial heart been implanted in a human being; this was done by Dr. Denton Cooley and the patient was supported by the artificial heart for a little less than three days, when he received a heart transplant.
Within the past year there have been about 15 cases in which air-driven left ventricular assist devices have been used in human patients. These assist devices have been intended as temporary assist devices and no patients have survived longer than one month after removal of these artificial hearts. None of the artificial hearts disclosed in the prior art has performed well enough to be considered acceptable for permanent replacement of the heart, or for long-term heart assist. Generally, devices which have included energy conversion systems have been very complicated, large, heavy and difficult to adapt to the necessary anatomical constraints. Some, or all, of these problems are apparent with devices such as the following: U.S. Pat. No. 3,842,440 utilizing a linear motor; U.S. Pat. No. 3,791,769 using magnetic forces across the skin; U.S. Pat. No. 3,563,028 using an implantable radioisotope-fueled Stirling Engine; U.S. Pat. No. 3,585,648 using ultrasonic energy; U.S. Pat. No. 3,774,243 using a carbohydrate- or hydrogen-fueled cell in combination with a storage battery to provide electric power for an artificial heart; U.S. Pat. No. 3,633,217 and No. 3,733,616 using electromagnetic actuators. Additional inventions are disclosed in the prior art which use electrohydraulic systems to convert electric power into hydraulic power and thereby actuate a diaphragm or other type blood pump, which have generally been complicated and heavy devices, as are the inventions disclosed in U.S. Pat. No. 3,636,570 and No. 3,048,165. Other electrohydraulic systems are disclosed in U.S. Pat. No. 3,572,979, No. 3,568,214, No. 3,148,624 and No. 3,783,453.